Herpes simplex virus causes a variety of human infections which are characterized by sporadic recurrences from latent foci. The wide variations in the clinical manifestations of this virus remain unexplained. Thirty percent of the adult population suffers from recurrent herpes labialis and although a smaller proportion of the population suffers from herpes keratitis, this virus remains a leading cause of corneal morbidity and blindness in the United States. The relationship of the eye and labial diseases and whether the eye infection may result from the labial infection has not been adequately examined. The proposed studies would seek to answer the question of whether the herpes virus strain causing the keratitis is the same strain causing the labialis and whether there is a relationship between the viral strain and the clinical course (severity, frequency of recurrence, provoking stimuli) of the infections. Patients with suspected herpes keratitis will have viral cultures taken from the eye, a blood sample drawn and a history concerning any prior herpes infection. Patients with other sites or prior herpetic disease, particularity labila involvement, will have viral cultures of these sites taken upon recurrences and the clinical course of these herpes infections will be followed. both viral isolates, eye and lip, will be grown in culture, the viral DNA labeled and then extracted. The DNA will be cleaved with restriction endonucleases and the fragments compared. The identity or non-identity of the two isolates will be determined. Correlations will be drawn from the DNA studies, the clinical courses of the eye and labial diseases and the neutralizing antibody titers. This information will provide the basis for futher studies concerning the pathogenesis of herpes keratitis, and may lead to preventive measures in the management of patients with herpes infections.